AST: Invent a mangling for Builtin.TheTupleType to appease incremental dependency tracking

Author: slavapestov

lib/AST/ASTMangler.cpp

@@ -1324,16 +1324,14 @@ void ASTMangler::appendType(Type type, GenericSignature sig,
       return appendType(ET->getConstraintType(), sig, forDecl);
     }
 
-    case TypeKind::BuiltinTuple:
-      llvm_unreachable("Not implemented");
-
     case TypeKind::UnboundGeneric:
     case TypeKind::Class:
     case TypeKind::Enum:
     case TypeKind::Struct:
     case TypeKind::BoundGenericClass:
     case TypeKind::BoundGenericEnum:
-    case TypeKind::BoundGenericStruct: {
+    case TypeKind::BoundGenericStruct:
+    case TypeKind::BuiltinTuple: {
       GenericTypeDecl *Decl;
       if (auto typeAlias = dyn_cast<TypeAliasType>(type.getPointer()))
         Decl = typeAlias->getDecl();
@@ -2476,6 +2474,9 @@ void ASTMangler::appendAnyGenericType(const GenericTypeDecl *decl) {
     return;
   }
 
+  if (nominal && isa<BuiltinTupleDecl>(nominal))
+    return appendOperator("BT");
+
   appendContextOf(decl);
 
   // Always use Clang names for imported Clang declarations, unless they don't

test/Incremental/Dependencies/tuple-member.swift

@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -primary-file %s -emit-reference-dependencies-path %t/tuple-members.swiftdeps
+
+func f() {}
+func f() -> S {}
+
+struct S {
+  var x: Int
+}
+
+_ = f().x